1. Field of the Invention
The present invention relates to a new method and apparatus that does not mandate the use of a drilling rig for repairing and structurally reinforcing tubular members that are next to a casing head assembly on an oil or gas well, and in one embodiment, casing string (or other conductors) contained inside of an outer drive pipe.
2. General Background of the Invention
In the oil and gas well drilling and production industry, casing arrangements are typically used as part of a well. These casing arrangements often include a smaller diameter inside production casing contained concentrically within the bore of a larger diameter surface casing string. There may be additional casing strings referred to as conductors. The outer most casing is referred to as a drive pipe. The production tube, surface casing, and conductors if present, are concentrically placed inside of an outermost drive pipe or like tubular member. A casing head assembly is provided at the top of the surface casing or conductor string. A grout filler often occupies the annulus that is in between the outer drive pipe and the inner casing strings to an elevation, if in a marine environment, somewhere in between the mud line and casing head assembly.
Such an assembly of drive pipe, casing strings, typically extend between the casing head assembly, which is what the wellhead or blow out preventor attaches to, and the oil or gas reservoir.
Moisture can accumulate from condensation, rain, etc. in between the outer drive pipe and inner casing string at the uppermost elevation. This creates a corrosion cell that can structurally weaken or perforate the conductor or surface casing. Often there are multiple conductors (in addition to the surface casing string) that are in between the outer drive pipe and the innermost production tubing. If there is only one conduit in between the outer drive pipe and the inner production tubing, it is typically referred to as the surface casing. Additional conduits in this area between outer drive pipe and surface casing are referred to as conductors. Historically, mobilization of a drilling rig has been required whenever repairs to one of the gas or oil well casing strings is needed.
Patents have issued that relate generally to the concept of a method and apparatus for protective encapsulation of structural members.
One early patent is the Papworth U.S. Pat. No. 4,068,483 entitled “Protective Sheath for Water-Eroded Wood Piling”. In the Papworth patent, the sheath is for a water-eroded wood piling. The sheath is a longitudinally split, flexible and resilient plastic casing with overlapping circumferentially end segments. The casing has a preformed, integral spout at its upper end into which wet concrete can be poured to fill the casing around the eroded section of the piling. Flexible bands clamp the casing tightly around the piling, and the spout has aligned openings in its opposite sides for passing the uppermost one of these bands. The casing may comprise two or more longitudinal sections in overlapped sealed engagement with each other end-to-end for enclosing a long eroded section of the piling.
In the Colbert U.S. Pat. No. 4,023,374, there is disclosed a repair sleeve for a marine pile and a method of applying same. The '374 patent discloses a preformed molded fiberglass resin plastic repair sleeve for use on a marine or other submerged concrete pile and a method of applying the same. The sleeve is provided with at least one vertical seam consisting of inside interlocking reentrant bends which together establish an interlocking tongue and groove joint. The joint is maintained effective by self-tapping screws which are in engaged relation with steel closure clips or strips. The sleeve after assembly is centered about the pile undergoing repair and the continuous space which exists between the sleeve and the pile is filled with a suitable grout which, when hardened, encompasses the internal or inside portions of the joint under pressure and prevents unfastening of the seam. The vertical longitudinal extend of the sleeve is somewhat greater than the water depth of the partially submerged pile to which it is applied and, where a cylindrical concrete pile is concerned, the sleeve is molded on an arcuate bias so as to present an open gap enabling the sleeve to be readily slipped sidewise onto the pile by one or more divers and the gap thereafter closed in order to effect the interlocked joint. Where a square pile is undergoing repair, the sleeve assumes a conformable four-sided shape or, alternatively, it may be formed of two mating right-angle sleeve sections having a pair of vertical inside interlocking joints or seams between their adjoining side margins.
The Straub U.S. Pat. No. 4,114,388 discloses a device for protecting a pile from ice formations collecting on it and subsequently abstracting the pile as a result of a variation of tide level including a tapered guard member secured to the pile. The guard member is firmly secured to the pile by interconnecting stiffening members, horizontal stiffening rings, vertical fin members and compression rings which also serve to prevent deformation of the guard member taper as a result of interaction with the ice formations. The guard member comprises two sections connected by vertically extending tongue and groove joints.
The Moore U.S. Pat. No. 4,306,821 discloses a system for the restoring and reconditioning of structural piling. The system provides an outer form which is attachable to a portion of the piling which has been eroded or corroded and has lost some of is thickness and thus its overall strength. A diameter building filler is placed into the intraform space between the form and the piling, the filler providing a protective and structural coating to that portion of the piling where corrosion or damage has taken place. In the preferred embodiment, the filler is a setting material such as a suitable epoxy.
Three patents have issued to Richard Snow and Milton Ellisor. These patents include U.S. Pat. Nos. 4,876,896; 4,892,410; and 4,993,876. The '896 and '410 patents discloses a method and apparatus for forming an encapsulation or encasement about a structural member that is said to be suited for use in a marine environment. A two-component polymer system for protective and repair encapsulation is pumpable in two separate strings to the location of the structural member to be encapsulated. The two reactive components are combined in a static mixer immediately prior to be injected within the surrounding translucent jacket. By combining the reactive components immediately prior to use, premature setup is avoided and the resulting grout may be directed to flow upwardly in the jacket for enhancing final properties. By suitable coloring of the components, visual monitoring of the final mixing and distribution in the translucent form or jacket of the encapsulation material may be monitored. A field test for determining bond strength of the encapsulation polymer to the structural member is also disclosed in the '876 patent and in the '410 patent. The '896 patent discloses a method of testing protective encapsulation of structural members.
The above discussed patents all relate primarily to coatings for protecting against corrosive effects of the surrounding marine environment. However, the prior art fails to address a problem of structural reinforcement for structural members that have become weak because of the corrosive and/or mechanical effects of the surrounding environment. Further, these patented prior art systems do not address concentric, pipe within pipe configurations.
Other patents that discuss repair methods are the Fox U.S. Pat. No. 4,091,301 and the Moran U.S. Pat. No. 967,952, both references cited in U.S. Pat. No. 6,536,991 naming applicants herein as inventors. U.S. Pat. No. 6,536,991 is incorporated herein by reference.